Drug abuse continues to be a major public health problem worldwide, with an estimated 1.6 million Americans confirming current cocaine use. There is evidence of sex differences in vulnerability to cocaine abuse, although males are disproportionately represented in research. This research project is a continuation of funded work aimed at understanding the neurobiology of cocaine abuse in a unique nonhuman primate model: intravenous cocaine self-administration in socially housed female monkeys. We have successfully combined the study of primate social behavior with intravenous drug self-administration and the noninvasive brain imaging procedure positron emission tomography (PET) to examine how environmental and pharmacological variables influence the behavioral and reinforcing effects of cocaine. Specific Aim 1 will examine the effects of chronic cocaine self-administration on dopamine (DA) D2/D3 receptors and DA transporters (DAT), brain systems that have been well characterized in males, but not females. Specific Aim 2 will examine whether acute social stress differentially affects cocaine self- administration as a function of social rank and whether dominant and subordinate females respond similarly to chronic drug treatment. Finally, in Specific Aim 3, we will combine environmental enrichment and chronic drug treatment in an effort to decrease the reinforcing strength of cocaine in dominant and subordinate monkeys. We hypothesize individual differences, based on social rank-induced differences in D2/D3 and DAT availability, in response to environmental challenges and drug treatments. The combination of social rank and PET imaging studied over years, in female monkeys, will allow for a better understanding of the interactions between social context and DA receptor function, which will be critical to developing behavioral and pharmacological treatment strategies.